Livestock are frequently troubled by various types of insects such as flies and lice that transmit infection of the skin, eyes, and ears as well as cause irritation leading to loss of production. Several approaches have been taken to alleviate this insect problem. One approach requires application of an insecticide spray on the livestock. This approach is undesirable because it requires a substantial amount of time and labor to gather and treat the livestock. Furthermore, this approach is effective for only a short period and requires frequent applications. A more economical and less labor-intensive approach is, therefore, generally preferred.
Another approach is the application of insecticide by contacting the target livestock with a device from which an insecticide is dispensed. Dispensers such as dust bags or oilers are placed in areas where it is anticipated that the livestock will come into contact with them. While this approach reduces the amount of labor involved in treating livestock, it does not ensure that each animal will receive the necessary treatment at regular intervals.
Yet another approach employs slow release pesticide mixed with a resinous substance that will release the insecticide over an extended period of time. These pesticide-containing resins have been used in a variety of forms ranging from collars to tags that are attached to various body parts of the animal. The use of pesticide-containing ear tags is of particular interest for treating livestock as is evident from the number of patents directed to such ear tags.
For example, U.S. Pat. Nos. 4,366,777 and 4,562,794 disclose ear tags in which a liquid insecticide dispenser is used. In U.S. Pat. No. 4,366,777, the liquid insecticide is enclosed in a fibrous or foam reservoir wicked onto the surface of the tag. In U.S. Pat. No. 4,562,794, the dispenser or reservoir containing the insecticide is attached to an animal identification tag. Release of the insecticide is dependent upon migration or diffusion of the insecticide through a semi-permeable membrane.
U.S. Pat. No. 4,428,327 discloses an insecticide-impregnated tape that is attached to a conventional ear tag. Each of these tags has been found to be disadvantageous because the insecticide containing reservoir or tape may be detached from the tag by fences or brush. It would, therefore, be advantageous to have a tag in which the insecticide is directly incorporated.
Such an approach is disclosed in U.S. Pat. Nos. 4,721,064; 4,195,075; and 4,265,876 as well as in Miller et al., (“Release of Pyrethroids from Insecticidal Ear Tags,” J. Econ. Entomol. 76:1335-1340, 1983) and Miller et al., (“Release Rates from Cattle Insecticidal Ear Tags in Various Regions of the United States,” The Southwestern Entomologist, Vol. II(1), pages 45-50, March 1986). The Miller et al. disclosures and U.S. Pat. No. 4,195,075 are, however, limited to liquid insecticides which can evaporate at ambient temperatures. Use of such liquid insecticides may be undesirable in areas where the ambient temperature is high enough to cause rapid evaporation of the insecticide and thus, result in an undesirably greater release of insecticide over a shorter period of time.
More specifically, U.S. Pat. No. 4,265,876 is limited to tags containing pyrethroid insecticides whereas coumaphos is not a pyrethroid. U.S. Pat. No. 5,018,481 discloses an insect control device, attachable to the body of a target animal, that has been formed from a powder mixture of coumaphos, polyvinyl chloride, and a plasticizer. The coumaphos is used in an amount of 5 to 30% of the device.
In order for the device to have a prolonged use of about four or more months of effective control of insects especially on cattle, a large concentration of insecticide must be incorporated into the carrier. If too much insecticide is used in plastic molded carriers, for example, in the form of ear tags, they become unsuitably soft. By the present invention, there is provided a suitable device for providing prolonged and effective insecticidal activity.